21641920 has 28 divisors (see below), whose sum is σ = 51535584. Its totient is φ = 8656640.

The previous prime is 21641909. The next prime is 21641933. The reversal of 21641920 is 2914612.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33496 + ... + 34135.

Almost surely, 2^21641920 is an apocalyptic number.

21641920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21641920 is an abundant number, since it is smaller than the sum of its proper divisors (29893664).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21641920 is an equidigital number, since it uses as much as digits as its factorization.

21641920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67648 (or 67638 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21641920 is about 4652.0877033865. The cubic root of 21641920 is about 278.6753760038.

The spelling of 21641920 in words is "twenty-one million, six hundred forty-one thousand, nine hundred twenty".